Ben Jackson wrote:
It's clearly important to the circuit (empirically) but I don't understand
what they're doing. I can sort of see C20 (the unmarked second one) acting
as a high-pass RC filter.

--
Ben Jackson AD7GD

http://www.ben.com/

Andy writes:

Well, it could be that his transmitter oscillated, and he just tacked

a 220 pf to ground for C20 to make it stop.......

Putting a cap to ground on the output of an op amp is something
I have always avoided, EXCEPT when it made things work... :)))))

Andy W4OAH